Apparatus for clarifying liquid

ABSTRACT

The effectiveness of a liquid clarifier having two liquid filled compartments, the first for depositing solids suspended in an incoming liquid solution on a continuous screen and the second for removing the solids from the same continuous screen, is optimized by preventing carry-over of water via the screen from the first compartment to the second by squeezing, wiping, drawing, or blowing the water off the screen as it emerges from the first compartment and by preventing carry-back of the solids from the second compartment to the first by spraying, wiping, blowing, or brushing the solids off the screen as it emerges from the second compartment.

United States Patent [19] Palmer et al.

[ APPARATUS FOR CLARIFYING LIQUID [75] Inventors: Warren G. Palmer,Saratoga, Calif.; Roger Davidson, Arlington Heights,

[73] Assignee: FMC Corporation, San Jose, Calif.

[22] Filed: Apr. 15, 1971 [21] Appl. No.: 134,334

Wells 210/396 X Bird [4s] Aug. 28, 1973 2,949,187 8/1960 Owens 210/386 X2,294,179 8/1942 Hawley..... 210/396 X 3,489,679 1/1970 Davidson et al.210/77 X [5 7] ABSTRACT The effectiveness of a liquid clarifier havingtwo liquid filled compartments, the first for depositing solidssuspended in an incoming liquid solution on a continuous screen and thesecond for removing the solids from the same continuous screen, isoptimized by preventing carry-over of water via the screen from thefirst compartment to the second by squeezing, wiping, drawing, orblowing the water off the screen as it emerges from the firstcompartment and by preventing carry-back of the solids from the secondcompartment to the first by spraying, wiping, blowing, or brushing thesolids off the screen as it emerges from the second compartment.

10 Claims, 15 Drawing Figures 5 Sheets-Shunt l O INVENTORS WARREN G.PALMER ROGER DAVIDSON BY 4244A, $1M

mania/5W4 ATTORNEYS Patented Aug. 28, 1973 5 Sheets-Sheet 2 INVENTORSWARREN G. PALMER ROGER DAVIDSON BY AJLW/ A? M /wdn ATTORNEYS PatentedAug. 28, 1973 5 Sheets-Sheet 5 INVENTORS WARREN G. PALMER I ROGERDAVIDSON BY M, Ara/Wax,

ATTORNEYS 5 Sheets-Sheet 4 |4 INVENTORS Z WARREN s. PALMER ROGERDAVIDSON LQMA, %M M JNQ ATTORNEYS Patented Aug. 28, 1973 3,754,661

5 Sheets-Sheet b ,1 INVENTORS WARREN G. PALMER F i fi l ROGER DAVIDSON IBYQ @19 NW 644N114" ATTORNEYS APPARATUS FOR CLARIFYING LIQUID BACKGROUNDOF THE INVENTION This invention relates generally to the removal of Amatter from a moving screen, but relates more particularly to theremoval of liquid from solids deposited on a moving screen and thesubsequent removal of the solids from the screen in a clarifyingapparatus such as the one disclosed in [1.8. Pat. No. 3,489,679, whichis of common ownership with the present application.

The apparatus with which the present invention is adapted to cooperatefinds particular application in the clarification of liquids containingminute particles of suspended solids including organic materials whichare normally difficult to remove from the host liquid. An example of ahost liquid would be sewage. The apparatus typically has a continuousscreen which circulates through a main compartment where solids from anincoming effluent are deposited thereon. After solid deposition, thecontinuous screen emerges from the effluent in the main compartment andcirculates through a second compartment where the solids are removed.Following removal of the solids in the second compartment, the screenemerges therefrom and returns to the main compartment to begin a newcycle. The apparatus in its basic form, without the aid of the presentinvention, may not operate at optimum potential because the screen as itemerges from the main compartment tends to pick up water, in addition tothe desired solid pickup, and deposits the water in the secondcompartment. Also, as the screen emerges from the second compartment, ittends to drag some of the solids which were to be deposited in thesecond compartment back into the main compartment, cutting down theeffectiveness and efficiency of the apparatus.

v SUMMARY OF THE INVENTION An object of the apparatus is to separate thesolids from the liquid in the first compartment, which solids are thencollected in the second compartment. Therefore, the effectiveness of theapparatus is improved if the liquid from the first compartmentisprevented from being transferred to the second compartment where thesolids are to be concentrated. Some provision may be made for preventingthe carry-over of liquid, since as the screen emerges from the firstliquid filled compartment where the solids were deposited on the screen,quantities of the liquid are carried with the solids.

In accordance with the present invention, excess liquid is returned tothe first compartment and thus prevented from being transferred to thesecond compartment while not deterring the transfer of solids betweenthe first and second compartments. This can be accomplished in variousways, including the placing of a backup roller against the screen on theside where the solids have been collected to retain them on the screen,while removing the excess liquid from the opposite or clean side of thescreen as it emerges from the first compartment. Removal of excessliquid is achieved by squeezing the liquid off the screen with a secondroller, wiping it off with a sponge or wick, drawing it off with avacuum head, blowing it off with air jets, or soaking it up with asponge roller. This procedure very effectively removes the excess liquidfrom the screen and, at the same time; insures the adherence of thesolids to the screen for transfer to the second compartment.

After the removal of liquid by one of the various ways discussed above,the solid bearing screen is submerged in a second compartment orcleaning compartment for the removal of the solids. Since it is aprimary object of the clarifying apparatus to concentrate solids in thecleaning compartment, it is important to the effective operation of theapparatus that all of the solids carried by the screen be removed anddeposited in the cleaning compartment and the screen itself be cleaned.To this end, the solids are removed in the second compartment by someapparatus, such as by an ultrasonic transducer. Also, to assure that thescreen is clean before it reenters the main chamber, various screencleaning devices may be employed immediately above the liquid of thecleaning compartment in the path of the screen after it leaves thecleaning compartment. These could include a set of spray noz zles placedon both sides of the screen to wash the solids off, wipers placed onboth sides of the screen to wipe the solids off, air jets placed on bothsides to blow the solids off, or soft counterrotating brushes placed onboth sides of the screen to brush the solids off.

The manner by which the advantages of the invention may be attained willbe apparent from the accompanying drawings and a detailed description ofthe invention which follows.

BRIEF DESCRIPTION OF THE DRAWINGS ratus for clarifying liquidsillustrating other embodi ments of the present invention;

FIG. 5 is a sectional view taken on line 5-5 of FIG. Y

FIG. 6 is a sectional view taken on line 6-6 of FIG. 4; 1

FIG. 7 is a vertical diagrammatic section of an apparatus forclarifying'liquids illustratingstill other embodiments of the presentinvention;

FIG. 8 is a sectional view taken on line 88 of FIG.

FIG. 9 is a sectional view taken on line 9-9 of FIG.

FIG. 10 is a diagrammatic vertical section of an apparatus forclarifying liquids illustrating still other embodiments of the presentinvention;

FIG. 11 is a sectional view taken on line 11-11 of FIG. 10;

FIG. 12 is a sectional view taken on line 12-12 of FIG. 10;

FIG. 13 is a diagrammatic vertical section of an apparatus forclarifying liquids illustrating still other embodiments of the presentinvention;

FIG. 14 is a sectional view taken on line 14 14 of FIG. 13; and

FIG. 15 is an elevational view, taken looking in the direction of arrow1515 of FIG. 13, showing in dotted lines the bottom configuration of thescreen cleaning compartment.

DESCRIPTION OF PREFERRED EMBODIMENT This invention will be described indetail in connection with a liquid clarifying apparatus generallydesignated 9 because it is with an apparatus of this type that theinvention is particularly useful.

The liquid clarifier 9 is comprised of a tank 14 divided into two liquidcompartments by a partition wall 10. The tank includes a maincompartment 11, where liquid suspended solids are received through aninlet 44 and in which a movable endless screen 13 is located, whichscreen filters out the solids from the effluent passing therethrough.Located on the other side of the wall 10 is a screen cleaning orconcentrating compartment 12 where the solids deposited on the screenare removed therefrom.

As shown in FIG. 1, the screen 13 is directed around a drum 22 and aseries of idler pulleys 15. It is in the area where the screen isdirected around the drum that solids suspended in an incoming solutionare deposited on the screen. It will be seen that the idler pulleys 15are so located that the screen moves out of the com partment 1 1 overthe partition wall 10, through the liquid containing portion of thecompartment 12, back into compartment 11, and around the drum 22. Due tothe differences in liquid levels maintained between the exterior andinterior parts of the drum, the effluent received in the maincompartment 11 through the inlet 44 is filtered by the screen 13 and theclarified liquid moves into the interior of the drum and flows outtherefrom through a conduit (not shown).

A suitable material for the screen 13 is a-filter cloth or woven fabric,such as a Polyester monofilament cloth with a nominal hole size of aboutmicrons. The

screen is power-driven by motor means, which are not 7 shown, but whichcan be of any conventional design, such as that illustrated in U.S. Pat.No. 3,489,679. The screen transfers the solids deposited thereon out ofthe main compartment 11 into the concentrating compartment 12, where thesolids are removed and the screen cleaned, preferably by an ultrasonictransducer 45, one

type of which is described in detail in the aforementioned U.S. Pat. No.3,489,679. After the screen is cleaned in the concentrating compartment12, it is then returned to the main compartment 11, where it will againfunction to filter the solids out of the effluent contained therein.

In accordance with the present invention, there are various meanslocated immediately above the liquid level in the main compartment 11for removing and returning into compratment l1 excess liquid which hasclung to the screen or is contained in the solids deposited on thescreen and being carried out of compartment 1 1 into compartment 12,where they are to be removed. It is desirable to return any such excessliquid to compartment 1 1, so that the liquid is retained in the maincompartment and not carried over into the concentrating compartment. Theseveral means that are employed for removing the excess liquid aredesignated by the numeral 16 in the various views in the drawingsandthey will be discussed in detail below.

As can be seen in FIGS. 1 and 2, liquid removal means 16 in oneembodiment comprises a cylindrical roller element 17 having a relativelyhard outer surface and extending across the entire width of screen 13.The roller 17 is disposed in pressing contact with the screen againstthe side of the screen on which solid matter is deposited. On theopposite side of the screen 13, there is located a set of air-jetnozzles which may take the form of orifices in a header 18, whichnozzles are disposed to direct streams of air against the relativelyclean side of the screen in a direction generally opposite to themovement of the screen 13 which is indicated by arrows in FIG. 1. Theroller 17 acts to hold the deposited solid matter against the screenwhile the air jets blow excess liquid, which has clung to the screen,off the screen and back into main compartment 11.

Modified embodiments of various means 16 that can be used to removeliquid that has adhered to the screen or is retained by the solids areshown in FIGS. 4, 7, l0 and 12. As can be seen, all of the illustratedembodiments employ a roller member 17 identical with that shown in theembodiment of FIGS. 1 and 2. While this roller element has been used inseveral of the embodiments for holding the solids against the screenwhile some other element removes the excess liquid, the invention isclearly not restricted to the use of such a roller. 7

In the embodiment illustrated in FIGS. 4 and 5, the means for removingthe liquid is shown to be a wiper 19 which simply acts to wipe excessliquid off the screen. This wiper 19 can be a squeegee, wick, sponge, orany other element suitable for wiping liquid off a mesh surface. Thewiper 19 is mounted on a transverse bar 47 (see FIG. 6) located on theopposite side of the screen from roller 17. The roller 17 is in pressingrelationship with the screen, and is located directly opposite to theroller 17 to remove liquid from the screen vhile the roller preventsdeposited solids from being removed.

The embodiment of the liquid remover means shown in FIGS. 7 and 8comprises two roller members. Roller member 17 in this embodiment isplaced on the clean side of screen 13 and a second roller member 20similar to roller member 17 but having a softer outer surface is placedon the solid bearing side for retention of the solids. The two rollermembers, one on either side of the screen, press in direct opposition toeach other thereby squeezing the excess liquid out of the screen whileleaving the solids attached.

Another embodiment of a liquid remover means is shown in FIGS. 10 and11. Here roller 17 is again disposed to press against the solid bearingside of screen 13 while directly opposed to roller 17 on the opposite orclean side of the screen is a sponge-coated roller 21 having arelatively hard core. Sponge roller 21 presses against the screen andabsorbs liquid off the screen. In order to free sponge roller 21 of theliquid it absorbs, a third roller 23 is placed in slightly overlappingrelationship therewith, to squeeze liquid from the sponge portion andcause it to drain back into the main compartment. The spacing betweenthe parallel rotational axes of rollers 21 and 23 is less than the sumof their respective radii, but not so much less that roller 23 couldever come into contact with the hard core of roller 21. Roller 23 isalso placed so as not to interfere with the cooperative squeezing ofrollers 17 and 21.

Another embodiment of a liquid removing means is illustrated in FIGS. 13and 14. In this embodiment, a roller 17 is again placed in pressingcontact against the solids bearing side of screen 13. A vacuum head 25,connected to a suitable vacuum header 26, is disposed on the opposite orclean side of screen 13 directly opposite the place at which roller 17presses against the screen. This vacuum head 25 acts to draw excessliquid off the screen while roller 17 is holding the deposited solids onthe screen for transfer to compartment 12.

After the excess liquid has been removed from screen 13, the screen isdirected into concentration compartment 12 with the solid matter stillattached. The purpose of concentrating compartment 12 is to remove thissolid matter and prevent it from redepositing itself on the screen.Preferably the solids are removed from the screen by an ultrasonictransducer; but other suitable removal means can be used. It is a commonoccurrence that not all of the solids get removed from the screen orthat some of the solids that do get removed re-attach themselves to thescreen before it leaves the concentrating compartment.

As stated above, one objective of the clarifying apparatus is toseparate the suspended solids in compartment 11 from the liquid in thatcompartment. Another objective is the concentration of solids inconcentrating compartment 12. Therefore, it is important that none ofthe solids which have been carried on the screen from compartment 11 tocompartment 12 be carried back into compartment 11. To prevent thiscarry-back, which would considerably reduce the effectiveness andefficiency of the clarifying apparatus, solid removal means 27 areprovided immediately above the liquid level of the concentratingcompartment 12.

FIGS. 1 and 3 show one preferred embodiment of solid removal means 27which is located above the liquid in compartment 12. It is comprised oftwo sets of air jets 29 flowing from pressurized headers 31 anddisposed, one set on either side of screen 13, so that the air streamsare directed to oppose the movement of the screen which is indicated byarrows in FIG. 1. As can be seen in FIG. 3, the air jets extend acrossthe entire width of screen 13 and serve to blow solids off the screenand back into concentrating compartment 12. The jets contact the screenafter the screen leaves compartment l2 and just prior to it re-enteringcompartment 1].

Another embodiment of solid removal means 27 is illustrated in FIGS. 4and 6. In this embodiment, a pair of wipers 33 are mounted on transversebars 34 located on both sides of screen 13. The wipers 33 press againstscreen 13 and wipe off any solids that are attached thereto. Thesewipersare preferably made of rubber, but any material suitable forwiping solid particles off a mesh surface could be used.

FIGS. 7 and 9 illustrate another means for removing solid matter from amoving screen. These consist of two sets of nozzles 35 connected towater supply conduits 37 and adapted to deliver a spray of water in adirection opposite to the movement of the screen 13. The water spraywashes the solid particles off the screen and back into compartment 12.The water supply conduits are of course connected to water pump means,which are not shown, to supply the proper amount of water at the desiredpressure.

Another embodiment of apparatus for removing solids from a moving screenis illustrated in FIGS. and

12. In this embodiment, two soft counter-rotating cylindrical brushes39, driven by motor means, not shown, are mounted from sidewalls of thetank, one on either side Of screen 13, so as to brush solids off thescreen and back into compartment 12.

The prevention of the re-attachment of solids to screen 13 after theyhave been removed therefrom can be aided by encouraging a rapid descentof the solids as they are removed from the screen. A rapid descent helpsto prevent re-attachment because, as can be seen in FIGS. 1, 4, 7, 10,and 13, the screen is onlysubmerged in the upper portion of compartment12, and if the removed solid particles are encouraged to descendrapidly, they move away from the upper portion of the compartment, thusdecreasing the possibility of re-attachment. Providing concentrationcompartment 12 with a hopper bottom 41 defined by inclined sidewalls 42,partition wall 10, and an end wall of the tank, as shown in FIG. 15, isa preferred way to encourage solid descent and compaction in the gravitysettling compartment.

Another way of preventing the re-attachment of the solids in compartment12 to the screen is to place a partially submerged wall or baffel 43 inclose proximity to the screen at the point where it emerges from theliquid to prevent the lighter solids, which have floated to the surface,from coming into contact with the screen.

In operation, a liquid having solids suspended therein flows throughinput conduit 44 into the main compartment ll of the liquid clarifier10. The endless movable screen 13 circulates through the maincompartment 11 and solids which are suspended in the incomingliquidcollect on one surface of the screen. The screen is moved out ofthe liquid in the main compartment 11 by motor means and it passesthrough a liquid removing means 16 which absorbs, wipes, blows, draws,or

squeezes the excess liquid from the solids and off the screen and drainsit back into the liquid in the main compartment 11. The removal of theliquid is accomplished without disturbing the solids which werecollected on the screen. The screen then moves into the concentrating orcleaning compartment 12 where most of the solids are removedultrasonically and encouraged to concentrate in the hopper bottom ofcompartment 12. As screen 13 emerges from the compartment 12, it passesthrough solid removal means 27 where any solids which remain on thescreen, or have re-attached, are washed, wiped, blown, or brushed offthe screen and back into compartment 12, where they drop to the hopperbottom of the compartment to be removed from the clarifying apparatusthrough conduit 46. The screen 13 then returns to main compartment 11free of any attached solids to begin an identical cycle.

Although various modes for carrying out the present invention have beenherein shown and described, it will be apparent that modification andvariation may be made without departing from what is regarded to be thesubject matter of the invention.

What is claimed is:

1. Apparatus for clarifying a liquid suspension of solids comprising amain liquid containing compartment having an inlet for unclarifiedliquid suspension and an outlet for clarified liquid, and a liquidcontaining auxiliary compartment; an endless screen in said maincompartment for filtering out suspended solids in said liquid suspensionas the liquid flows between said inlet and outlet, which screen extendsthrough the liquids contained in both compartments; means for movingsaid screen for the transfer of screened solids from the main to theauxiliary compartment; first means located above the liquid in said maincompartment for removing liquid carried by the screen and solids on thescreen out of the main compartment while retaining the solids on saidscreen; second means for cleaning said screen as it enters saidauxiliary compartment; and third means for cleaning said screen after itleaves said auxiliary compartment to insure that no solids will becarried back into said main compartment.

2. The apparatus of claim 1 wherein said first means comprises a firstroller member contacting said screen, a second roller member contactingthe screen on the opposite side thereof and at a position which isdirectly opposed to the first roller so as to squeeze the screen betweenthe first and second rollers, thereby acting to force the excess liquidoff the screen and back into the main compartment.

3. The apparatus of claim 1, wherein the first means comprises rollerand wiper members acting in pressing relationship on opposite sides ofthescreen, with the roller member being disposed on the side where thesolids have been collected to wipe excess liquid off the screen, whichthen drops back into the main compartment.

4. The apparatus of claim I, wherein the first means comprises a rollermember contacting the screen memher on the side where the solids havebeen collected and a vacuum head member directly opposing the rollermember on the opposite side of the screen to draw excess liquid off thescreen.

5. The apparatus of claim 1 wherein said first means comprises a rollermember contacting the screen and air jet means, said air jet means beingdisposed on the opposite side of the screen from the roller member so asto direct streams of air against the motion of the belt directlyopposite to where the roller member contacts the screen so as to blowexcess liquid off the screen and back into the main compartment.

6. The apparatus of claim 1 wherein said first means comprises a firstroller member contacting the screen, a second hard cored resilientsurfaced roller member disposed on the opposite side of the screen incontact with the screen member and directly opposing the first roller tosqueeze the screen between said first and second roller member andabsorb the excess water off the screen, and a third roller memberdisposed in a pressing relationship to the second roller member so asnot to interfere with the squeezing action of the first and secondroller members but so as to squeeze the liquid out of the second rollerand cause the liquid to drop back into the main compartment.

7. The apparatus of claim 1, wherein said third means comprises a set ofnozzles disposed on opposite sides of the screen, through which a liquidcan be sprayed to wash any solids remaining on the screen back into theauxiliary compartment.

8. The apparatus of claim 1, wherein said third means comprises wipermeans disposed on opposite sides of the screen in pressing contacttherewith to wipe any solids remaining on the screen back into theauxiliary compartment.

9. The apparatus of claim 1, wherein the third means comprises air jetmeans disposed on opposite sides of the screen to blow solids remainingon the screen off the screen and back into the auxiliary compartment.

10. The apparatus of claim 1, wherein said third means comprises softcounter-rotating brushes disposed on opposite sides of the screen incontact therewith to brush solids remaining on the screen back into theauxiliary compartment.

* i t III

1. Apparatus for clarifying a liquid suspension of solids comprising amain liquid containing compartment having an inlet for unclarifiedliquid suspension and an outlet for clarified liquid, and a liquidcontaining auxiliary compartment; an endless screen in said maincompartment for filtering out suspended solids in said liquid suspensionas the liquid flows between said inlet and outlet, which screen extendsthrough the liquids contained in both compartments; means for movingsaid screen for the transfer of screened solids from the main to theauxiliary compartment; first means located above the liquid in said maincompartment for removing liquid carried by the screen and solids on thescreen out of the main compartment while retaining the solids on saidscreen; second means for cleaning said screen as it enters saidauxiliary compartment; and third means for cleaning said screen after itleaves said auxiliary compartment to insure that no solids will becarried back into said main compartment.
 2. The apparatus of claim 1wherein said first means comprises a first roller member contacting saidscreen, a second roller member contacting the screen on the oppositeside thereof and at a position which is directly opposed to the firstroller so as to squeeze the screen between the first and second rollers,thereby acting to force the excess liquid off the screen and back intothe main compartment.
 3. The apparatus of claim 1, wherein the firstmeans comprises roller and wiper members acting in pressing relationshipon opposite sides of the screen, with the roller member being disposedon the side where the solids have been collected to wipe excess liquidoff the screen, which then drops back into the main compartment.
 4. Theapparatus of claim 1, wherein the first means comprises a roller membercontacting the screen member on the side where the solids have beencollected and a vacuum head member directly opposing the roller memberon the opposite side of the screen to draw excess liquid off the screen.5. The apparatus of claim 1 wherein said first means comprises a rollermember contacting the screen and air jet means, said air jet means beingdisposed on the opposite side of the screen from the roller member so asto direct streams of air against the motion of the belt directlyopposite to where the roller member contacts the screen so as to blowexcess liquid off the screen and back into the main compartment.
 6. Theapparatus of claim 1 wherein said first means comprises a first rollermember contacting the screen, a second hard cored resilient surfacedroller member disposed on the opposite side of the screen in contactwith the screen member and directly opposing the first roller to squeezethe screen between said first and second roller member and absorb theexcesS water off the screen, and a third roller member disposed in apressing relationship to the second roller member so as not to interferewith the squeezing action of the first and second roller members but soas to squeeze the liquid out of the second roller and cause the liquidto drop back into the main compartment.
 7. The apparatus of claim 1,wherein said third means comprises a set of nozzles disposed on oppositesides of the screen, through which a liquid can be sprayed to wash anysolids remaining on the screen back into the auxiliary compartment. 8.The apparatus of claim 1, wherein said third means comprises wiper meansdisposed on opposite sides of the screen in pressing contact therewithto wipe any solids remaining on the screen back into the auxiliarycompartment.
 9. The apparatus of claim 1, wherein the third meanscomprises air jet means disposed on opposite sides of the screen to blowsolids remaining on the screen off the screen and back into theauxiliary compartment.
 10. The apparatus of claim 1, wherein said thirdmeans comprises soft counter-rotating brushes disposed on opposite sidesof the screen in contact therewith to brush solids remaining on thescreen back into the auxiliary compartment.